The attributes got renamed in PR #126440 and in some places this caused
evaluation errors, e.g. the tarball job was saying (locally)
> attribute 'alsaUtils' missing, at /build/source/nixos/modules/services/audio/alsa.nix:6:4
and I suspect that trunk-combined jobset's failure to evaluate was also caused.
The distinction between the inputs doesn't really make sense in the
mkShell context. Technically speaking, we should be using the
nativeBuildInputs most of the time.
So in order to make this function more beginner-friendly, add "packages"
as an attribute, that maps to nativeBuildInputs.
This commit also updates all the uses in nixpkgs.
In my opinion Functions should only contain pure functions. These are
both meant to provide derivations so I put them under Builders. Don't
know exactly *where* to put them so "special" it is...
